Golang : Saving private and public key to files

In this tutorial we will learn how to save the RSA private and public keys to files. We will use RSA in this tutorial, but you can use this tutorial for saving other type of encryption system private and public keys.

Without further ado :

saversafiles.go

 package main

 import (
 "os"
 "fmt"
 "crypto/rand"
 "crypto/rsa"
 "encoding/gob"
 "encoding/pem"
 "crypto/x509"
 )

 func main() {

 // generate private key
 privatekey, err := rsa.GenerateKey(rand.Reader, 1024)

 if err != nil {
 fmt.Println(err.Error)
 os.Exit(1)
 }

 var publickey *rsa.PublicKey
 publickey = &privatekey.PublicKey

 // save private and public key separately
 privatekeyfile, err := os.Create("private.key")
 if err != nil {
 fmt.Println(err)
 os.Exit(1)
 }
 privatekeyencoder := gob.NewEncoder(privatekeyfile)
 privatekeyencoder.Encode(privatekey)
 privatekeyfile.Close()


 publickeyfile, err := os.Create("public.key")
 if err != nil {
 fmt.Println(err)
 os.Exit(1)
 }

 publickeyencoder := gob.NewEncoder(publickeyfile)
 publickeyencoder.Encode(publickey)
 publickeyfile.Close()

 // save PEM file
 pemfile, err := os.Create("private.pem")

 if err != nil {
 fmt.Println(err)
 os.Exit(1)
 }

 // http://golang.org/pkg/encoding/pem/#Block
 var pemkey = &pem.Block{
 Type : "RSA PRIVATE KEY",
 Bytes : x509.MarshalPKCS1PrivateKey(privatekey)}

 err = pem.Encode(pemfile, pemkey)

 if err != nil {
 fmt.Println(err)
 os.Exit(1)
 }

 pemfile.Close()

 }

Note : The repeatable codes can be converted to function for easier calling.

Sample output of private.pem :

-----BEGIN RSA PRIVATE KEY-----

MIICXAIBAAKBgQC9/H127GOFgwROUPTGdpw6fCL5DGvpldLALkr6o7ia/6mvioVT

B+ivUwgo/WXyIHHPEtKNtnKH4OUcav/TNiXDqV+q9ybZ6SCodHPtryJzyy3iMhRz

9WxfAlKrF+XmiC8hzJsXjfE3o0sjacrEdlxn+zmxu5H2weSFh4ZjXCBtzQIDAQAB

AoGAe1QfYga76ByPvAMjkn3GltSko0Uj/CMNB0JF3ARRvxR9430pZSf6LW3aGzm7

Zv0WxBR06Bdqq7gbImJ3JXW99vAqUUseLuR6KQ78YvZDkNz4aKnXCFBvJmtCVTj9

SPyY0KoKjeR7slgdik0CbrisqrlFOk+eO9Bj7Wd40p14SGECQQDCUp2/t9qS5v1O

C+1xkRZ+BDJ1+WBoGHDXFPVchbfYdZSHtlurTEdN8g4MaHohY7d7/QFUJSXOh4M8

utS0TmTpAkEA+kmGLrrAO+SDNJMcNi/w+m1qO1o3acewUbZI04tyqon583O+rVzB

Lo3iTbErKTK/1HA0+Brqjp7xe6lS0PyDRQJARjdWGw2TJFvlEcuLi+rSRsy7cxee

N18FfyJqmnkS+ltaRUOmkhoo9chOPTuPTftbNKkyTrZxl9Qtnscfzts46QJBAIf2

/Q/Rn7BpmOUsrXy6WnyQh88qWUP7mMsq7TEOZgJC5ifczs66vq8doLx37Gx7Bz7O

ndfSN2225pQ5DaY+JskCQHIrr7XOX0Ka0FmZcyvsDI0YzySvATrDnYxa3gj4YBSW

eaV15LvMgibF3khLjXsuR8kUNd58NB/uAyeXuGrF2sI=

-----END RSA PRIVATE KEY-----

Reference :

https://code.google.com/p/go/source/browse/src/pkg/encoding/pem/pem_test.go